Electro-chemical deposition system

ABSTRACT

The present invention provides an electro-chemical deposition system that is designed with a flexible architecture that is expandable to accommodate future designs and gap fill requirements and provides satisfactory throughput to meet the demands of other processing systems. The electro-chemical deposition system generally comprises a mainframe having a mainframe wafer transfer robot, a loading station disposed in connection with the mainframe, one or more processing cells disposed in connection with the mainframe, and an electrolyte supply fluidly connected to the one or more electrical processing cells. Preferably, the electro-chemical deposition system includes a spin-rinse-dry (SRD) station disposed between the loading station and the mainframe, a rapid thermal anneal chamber attached to the loading station, and a system controller for controlling the electro-chemical deposition process and the components of the electro-chemical deposition system.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of co-pending U.S. patentapplication Ser. No. 09/867,780, filed May 29, 2001, which is acontinuation of U.S. patent application Ser. No. 09/289,074, filed Apr.8, 1999, which claims benefit of U.S. Provisional patent applicationSer. No. 06/110,209, filed Nov. 30, 1998. Each of the aforementionedrelated patent applications is herein incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention generally relates to deposition of a metallayer onto a wafer/substrate. More particularly, the present inventionrelates to an electro-chemical deposition or electroplating system forforming a metal layer on a wafer/substrate.

[0004] 2. Description of the Related Art

[0005] Sub-quarter micron, multi-level metallization is one of the keytechnologies for the next generation of ultra large scale integration(ULSI). The multilevel interconnects that lie at the heart of thistechnology require planarization of interconnect features formed in highaspect ratio apertures, including contacts, vias, lines and otherfeatures. Reliable formation of these interconnect features is veryimportant to the success of ULSI and to the continued effort to increasecircuit density and quality on individual substrates and die.

[0006] As circuit densities increase, the widths of vias, contacts andother features, as well as the dielectric materials between them,decrease to less than 250 nanometers, whereas the thickness of thedielectric layers remains substantially constant, with the result thatthe aspect ratios for the features, i.e., their height divided by width,increases. Many traditional deposition processes, such as physical vapordeposition (PVD) and chemical vapor deposition (CVD), have difficultyfilling structures where the aspect ratio exceed 4:1, and particularlywhere it exceeds 10:1. Therefore, there is a great amount of ongoingeffort being directed at the formation of void-free, nanometer-sizedfeatures having high aspect ratios wherein the ratio of feature heightto feature width can be 4:1 or higher. Additionally, as the featurewidths decrease, the device current remains constant or increases, whichresults in an increased current density in the feature.

[0007] Elemental aluminum (Al) and its alloys have been the traditionalmetals used to form lines and plugs in semiconductor processing becauseof aluminum's perceived low electrical resistivity, its superioradhesion to silicon dioxide (SiO₂), its ease of patterning, and theability to obtain it in a highly pure form. However, aluminum has ahigher electrical resistivity than other more conductive metals such ascopper, and aluminum also can suffer from electromigration leading tothe formation of voids in the conductor.

[0008] Copper and its alloys have lower resistivities than aluminum andsignificantly higher electromigration resistance as compared toaluminum. These characteristics are important for supporting the highercurrent densities experienced at high levels of integration and increasedevice speed. Copper also has good thermal conductivity and is availablein a highly pure state. Therefore, copper is becoming a choice metal forfilling sub-quarter micron, high aspect ratio interconnect features onsemiconductor substrates.

[0009] Despite the desirability of using copper for semiconductor devicefabrication, choices of fabrication methods for depositing copper intovery high aspect ratio features, such as a 4:1, having 0.35 μ(or less)wide vias are limited. As a result of these process limitations,plating, which had previously been limited to the fabrication of lineson circuit boards, is just now being used to fill vias and contacts onsemiconductor devices.

[0010] Metal electroplating is generally known and can be achieved by avariety of techniques. A typical method generally comprises physicalvapor depositing a barrier layer over the feature surfaces, physicalvapor depositing a conductive metal seed layer, preferably copper, overthe barrier layer, and then electroplating a conductive metal over theseed layer to fill the structure/feature. Finally, the deposited layersand the dielectric layers are planarized, such as by chemical mechanicalpolishing (CMP), to define a conductive interconnect feature.

[0011]FIG. 1 is a cross sectional view of a simplified typical fountainplater 10 incorporating contact pins. Generally, the fountain plater 10includes an electrolyte container 12 having a top opening, a substrateholder 14 disposed above the electrolyte container 12, an anode 16disposed at a bottom portion of the electrolyte container 12 and acontact ring 20 contacting the substrate 22. A plurality of grooves 24are formed in the lower surface of the substrate holder 14. A vacuumpump (not shown) is coupled to the substrate holder 14 and communicateswith the grooves 24 to create a vacuum condition capable of securing thesubstrate 22 to the substrate holder 14 during processing. The contactring 20 comprises a plurality of metallic or semi-metallic contact pins26 distributed about the peripheral portion of the substrate 22 todefine a central substrate plating surface. The plurality of contactpins 26 extend radially inwardly over a narrow perimeter portion of thesubstrate 22 and contact a conductive seed layer of the substrate 22 atthe tips of the contact pins 26. A power supply (not shown) is attachedto the pins 26 thereby providing an electrical bias to the substrate 22.The substrate 22 is positioned above the cylindrical electrolytecontainer 12 and electrolyte flow impinges perpendicularly on thesubstrate plating surface during operation of the cell 10.

[0012] While present day electroplating cells, such as the one shown inFIG. 1, achieve acceptable results on larger scale substrates, a numberof obstacles impair consistent reliable electroplating onto substrateshaving micron-sized, high aspect ratio features. Generally, theseobstacles include providing uniform power distribution and currentdensity across the substrate plating surface to form a metal layerhaving uniform thickness, preventing unwanted edge and backsidedeposition to control contamination to the substrate being processed aswell as subsequent substrates, and maintaining a vacuum condition whichsecures the substrate to the substrate holder during processing. Also,the present day electroplating cells have not provided satisfactorythroughput to meet the demands of other processing systems and are notdesigned with a flexible architecture that is expandable to accommodatefuture designs rules and gap fill requirements. Furthermore, currentelectroplating system platforms have not provided post electro-chemicaldeposition treatment, such as a rapid thermal anneal treatment, forenhancing deposition results within the same system platform.

[0013] Additionally, current electroplating systems are incapable ofperforming necessary processing steps without resorting to peripheralcomponents and time intensive efforts. For example, analysis of theprocessing chemicals is required periodically during the platingprocess. The analysis determines the composition of the electrolyte toensure proper proportions of the ingredients. Conventional analysis isperformed by extracting a sample of electrolyte from a test port andtransferring the sample to a remote analyzer. The electrolytecomposition is then manually adjusted according to the results of theanalysis. The analysis must be performed frequently because theconcentrations of the various chemicals are in constant flux. However,the foregoing method is time consuming and limits the number of analyseswhich can be performed.

[0014] Therefore, there remains a need for an electro-chemicaldeposition system that is designed with a flexible architecture that isexpandable to accommodate future designs rules and gap fill requirementsand provides satisfactory throughput to meet the demands of otherprocessing systems. There is also a need for an electro-chemicaldeposition system that provides uniform power distribution and currentdensity across the substrate plating surface to form a metal layerhaving uniform thickness and maintain a vacuum condition which securesthe substrate to the substrate holder during processing. It would bedesirable for the system to prevent and/or remove unwanted edge andbackside deposition to control contamination to the substrate beingprocessed as well as subsequent substrates. It would also be desirablefor the system to include one or more chemical analyzers integrated withthe processing system to provide real-time analysis of the electrolytecomposition. It would be further desirable for the electro-chemicaldeposition system to provide a post electro-chemical depositiontreatment, such as a rapid thermal anneal treatment, for enhancingdeposition results.

SUMMARY OF THE INVENTION

[0015] The present invention generally provides an electro-chemicaldeposition system that is designed with a flexible architecture that isexpandable to accommodate future designs and gap fill requirements andprovides satisfactory throughput to meet the demands of other processingsystems. The electro-chemical deposition system generally comprises amainframe having a mainframe wafer transfer robot, a loading stationdisposed in connection with the mainframe, one or more processing cellsdisposed in connection with the mainframe, and an electrolyte supplyfluidly connected to the one or more electrical processing cells.Preferably, the electro-chemical deposition system includes aspin-rinse-dry (SRD) station disposed between the loading station andthe mainframe, a rapid thermal anneal chamber attached to the loadingstation, and a system controller for controlling the electro-chemicaldeposition process and the components of the electro-chemical depositionsystem.

[0016] One aspect of the invention provides an electro-chemicaldeposition system that provides uniform power distribution and currentdensity across the substrate plating surface to form a metal layerhaving uniform thickness and maintain a vacuum condition which securesthe substrate to the substrate holder during processing.

[0017] Another aspect of the invention provides an electro-chemicaldeposition system that prevents and/or remove unwanted edge and backsidedeposition to control contamination to the substrate being processed aswell as subsequent substrates.

[0018] Another aspect of the invention provides an apparatus forelectro-chemically depositing a metal onto a substrate comprising a headassembly having a cathode and a wafer holder, a process kit having anelectrolyte container and an anode, an electrolyte overflow catch and apower supply connected to the cathode and the anode. Preferably, thecathode includes a cathode contact ring, and the wafer holder includes abladder system that ensures proper contact of the cathode contact ringto the wafer. Preferably, the surfaces of the cathode contact ring thatare exposed to the electrolyte are coated or treated to provide ahydrophilic surface.

[0019] Yet another aspect of the invention provides a permeableencapsulated anode adapted to remove anode sludge and other particulatesgenerated by the dissolving anode. Preferably, the encapsulated anodecomprises a hydrophilic membrane that traps or filters the contaminatesfrom the electrolyte. The encapsulated anode also preferably includes abypass electrolyte inlet and a bypass outlet to facilitate flow of theelectrolyte inside the encapsulated anode.

[0020] Still another aspect of the invention provides an electrolytereplenishing system having a real-time chemical analyzer module and adosing module. The chemical analyzer module includes at least one andpreferably two analyzers operated by a controller and integrated with acontrol system of the electro-chemical deposition system. A sample lineprovides continuous flow of electrolyte from a main electrolyte tank tothe chemical analyzer module. A first analyzer determines theconcentrations of organic substances in the electrolyte while the secondanalyzer determines the concentrations of inorganic substances. Thedosing module is then activated to deliver the proper proportions ofchemicals to the main tank in response to the information obtained bythe chemical analyzer module.

[0021] Yet another aspect of the invention provides a postelectro-chemical deposition treatment, such as a rapid thermal annealtreatment, for enhancing deposition results. The apparatus for rapidthermal anneal treatment preferably comprises a rapid thermal annealchamber disposed adjacent the loading station of the electro-chemicaldeposition system.

[0022] Yet another aspect of the invention provides a rotatable headassembly for an electroplating cell that provides rotation of the waferduring processing to improve deposition uniformity. The rotatable headassembly also enhances removal of residual electrolytes from the waferholder assembly after the electroplating process. Preferably, thecomponents of the wafer holder assembly, including the inflatablebladder and the cathode contact ring has hydrophilic surfaces to enhancedripping and removal of the residual electrolyte.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] So that the manner in which the above recited features of thepresent invention can be understood in detail, a more particulardescription of the invention, briefly summarized above, may be had byreference to embodiments, some of which are illustrated in the appendeddrawings. It is to be noted, however, that the appended drawingsillustrate only typical embodiments of this invention and are thereforenot to be considered limiting of its scope, for the invention may admitto other equally effective embodiments.

[0024] So that the manner in which the above recited features,advantages and objects of the present invention are attained can beunderstood in detail, a more particular description of the invention,briefly summarized above, may be had by reference to the embodimentsthereof which are illustrated in the appended drawings.

[0025] It is to be noted, however, that the appended drawings illustrateonly typical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

[0026]FIG. 1 is a cross sectional view of a simplified typical fountainplater 10 incorporating contact pins.

[0027]FIG. 2 is a perspective view of an electroplating system platform200 of the invention.

[0028]FIG. 3 is a schematic view of an electroplating system platform200 of the invention.

[0029]FIG. 4 is a schematic perspective view of a spin-rinse-dry (SRD)module of the present invention, incorporating rinsing and dissolvingfluid inlets.

[0030]FIG. 5 is a side cross sectional view of the spin-rinse-dry (SRD)module of FIG. 4 and shows a substrate in a processing positionvertically disposed between fluid inlets.

[0031]FIG. 6 is a cross sectional view of an electroplating process cell400 according to the invention.

[0032]FIG. 7 is a partial cross sectional perspective view of a cathodecontact ring.

[0033]FIG. 8 is a cross sectional perspective view of the cathodecontact ring showing an alternative embodiment of contact pads.

[0034]FIG. 9 is a cross sectional perspective view of the cathodecontact ring showing an alternative embodiment of the contact pads andan isolation gasket.

[0035]FIG. 10 is a cross sectional perspective view of the cathodecontact ring showing the isolation gasket.

[0036]FIG. 11 is a simplified schematic diagram of the electricalcircuit representing the electroplating system through each contact pin.

[0037]FIG. 12 is a cross sectional view of a wafer assembly 450 of theinvention.

[0038]FIG. 12A is an enlarged cross sectional view of the bladder areaof FIG. 12.

[0039]FIG. 13 is a partial cross sectional view of a wafer holder plate.

[0040]FIG. 14 is a partial cross sectional view of a manifold.

[0041]FIG. 15 is a partial cross sectional view of a bladder.

[0042]FIG. 16 is a schematic diagram of an electrolyte replenishingsystem 220.

[0043]FIG. 17 is a cross sectional view of a rapid thermal annealchamber.

[0044]FIG. 18 is a perspective view of an alternative embodiment of acathode contact ring.

[0045]FIG. 19 is a partial cross sectional view of an alternativeembodiment of a wafer holder assembly.

[0046]FIG. 20 is a cross sectional view of a first embodiment of anencapsulated anode.

[0047]FIG. 21 is a cross sectional view of a second embodiment of anencapsulated anode.

[0048]FIG. 22 is a cross sectional view of a third embodiment of anencapsulated anode.

[0049]FIG. 23 is a cross sectional view of a fourth embodiment of anencapsulated anode.

[0050]FIG. 24 is a top schematic view of a mainframe transfer robothaving a flipper robot incorporated therein.

[0051]FIG. 25 is an alternative embodiment of the process head assemblyhaving a rotatable head assembly 2410.

[0052]FIG. 26a and 26 b are cross sectional views of embodiments of adegasser module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0053]FIG. 2 is a perspective view of an electroplating system platform200 of the invention. FIG. 3 is a schematic view of an electroplatingsystem platform 200 of the invention. Referring to both FIGS. 2 and 3,the electroplating system platform 200 generally comprises a loadingstation 210, a thermal anneal chamber 211, a spin-rinse-dry (SRD)station 212, a mainframe 214, and an electrolyte replenishing system220. Preferably, the electroplating system platform 200 is enclosed in aclean environment using panels such as plexiglass panels. The mainframe214 generally comprises a mainframe transfer station 216 and a pluralityof processing stations 218. Each processing station 218 includes one ormore processing cells 240. An electrolyte replenishing system 220 ispositioned adjacent the electroplating system platform 200 and connectedto the process cells 240 individually to circulate electrolyte used forthe electroplating process. The electroplating system platform 200 alsoincludes a control system 222, typically comprising a programmablemicroprocessor.

[0054] The loading station 210 preferably includes one or more wafercassette receiving areas 224, one or more loading station transferrobots 228 and at least one wafer orientor 230. The number of wafercassette receiving areas, loading station transfer robots 228 and waferorientor included in the loading station 210 can be configured accordingto the desired throughput of the system. As shown for one embodiment inFIGS. 2 and 3, the loading station 210 includes two wafer cassettereceiving areas 224, two loading station transfer robots 228 and onewafer orientor 230. A wafer cassette 232 containing wafers 234 is loadedonto the wafer cassette receiving area 224 to introduce wafers 234 intothe electroplating system platform. The loading station transfer robot228 transfers wafers 234 between the wafer cassette 232 and the waferorientor 230. The loading station transfer robot 228 comprises a typicaltransfer robot commonly known in the art. The wafer orientor 230positions each wafer 234 in a desired orientation to ensure that thewafer is properly processed. The loading station transfer robot 228 alsotransfers wafers 234 between the loading station 210 and the SRD station212 and between the loading station 210 and the thermal anneal chamber211.

[0055]FIG. 4 is a schematic perspective view of a spin-rinse-dry (SRD)module of the present invention, incorporating rinsing and dissolvingfluid inlets. FIG. 5 is a side cross sectional view of thespin-rinse-dry (SRD) module of FIG. 4 and shows a substrate in aprocessing position vertically disposed between fluid inlets.Preferably, the SRD station 212 includes one or more SRD modules 236 andone or more wafer pass-through cassettes 238. Preferably, the SRDstation 212 includes two SRD modules 236 corresponding to the number ofloading station transfer robots 228, and a wafer pass-through cassette238 is positioned above each SRD module 236. The wafer pass-throughcassette 238 facilitates wafer transfer between the loading station 210and the mainframe 214. The wafer pass-through cassette 238 providesaccess to and from both the loading station transfer robot 228 and arobot in the mainframe transfer station 216.

[0056] Referring to FIGS. 4 and 5, the SRD module 238 comprises a bottom330 a and a sidewall 330 b, and an upper shield 330 c which collectivelydefine a SRD module bowl 330 d, where the shield attaches to thesidewall and assists in retaining the fluids within the SRD module.Alternatively, a removable cover could also be used. A pedestal 336,located in the SRD module, includes a pedestal support 332 and apedestal actuator 334. The pedestal 336 supports the substrate 338(shown in FIG. 5) on the pedestal upper surface during processing. Thepedestal actuator 334 rotates the pedestal to spin the substrate andraises and lowers the pedestal as described below. The substrate may beheld in place on the pedestal by a plurality of clamps 337. The clampspivot with centrifugal force and engage the substrate preferably in theedge exclusion zone of the substrate. In a preferred embodiment, theclamps engage the substrate only when the substrate lifts off thepedestal during the processing. Vacuum passages (not shown) may also beused as well as other holding elements. The pedestal has a plurality ofpedestal arms 336 a and 336 b, so that the fluid through the secondnozzle may impact as much surface area on the lower surface of thesubstrate as is practical. An outlet 339 allows fluid to be removed fromthe SRD module. The terms “below”, “above”, “bottom”, “top”, “up”,“down”, “upper”, and “lower” and other positional terms used herein areshown with respect to the embodiments in the figures and may be varieddepending on the relative orientation of the processing apparatus.

[0057] A first conduit 346, through which a first fluid 347 flows, isconnected to a valve 347 a. The conduit may be hose, pipe, tube, orother fluid containing conduits. The valve 347 a controls the flow ofthe first fluid 347 and may be selected from a variety of valvesincluding a needle, globe, butterfly, or other valve types and mayinclude a valve actuator, such as a solenoid, that can be controlledwith a controller 362. The conduit 346 connects to a first fluid inlet340 that is located above the substrate and includes a mounting portion342 to attach to the SRD module and a connecting portion 344 to attachto the conduit 346. The first fluid inlet is shown with a single firstnozzle 348 to deliver a first fluid 347 under pressure onto thesubstrate upper surface. However, multiple nozzles could be used andmultiple fluid inlets could be positioned about the inner perimeter ofthe SRD module. Preferably, nozzles placed above the substrate should beoutside the diameter of the substrate to lessen the risk of the nozzlesdripping on the substrate. The first fluid inlet could be mounted in avariety of locations, including through a cover positioned above thesubstrate. Additionally, the nozzle may articulate to a variety ofpositions using an articulating member 343, such as a ball and socketjoint.

[0058] Similar to the first conduit and related elements describedabove, a second conduit 352 is connected to a control valve 349 a and asecond fluid inlet 350 with a second nozzle 351. The second fluid inlet350 is shown below the substrate and angled upward to direct a secondfluid under the substrate through the second nozzle 351. Similar to thefirst fluid inlet, the second fluid inlet may include a plurality ofnozzles, a plurality of fluid inlets and mounting locations, and aplurality of orientations including using the articulating member 353.Each fluid inlet could be extended into the SRD module at a variety ofpositions. For instance, if the flow is desired to be a certain anglethat is directed back toward the SRD module periphery along the edge ofthe substrate, the nozzles could be extended radially inward and thedischarge from the nozzles be directed back toward the SRD moduleperiphery.

[0059] The controller 362 could individually control the two fluids andtheir respective flow rates, pressure, and timing, and any associatedvalving, as well as the spin cycle(s). The controller could be remotelylocated, for instance, in a control panel or control room and theplumbing controlled with remote actuators. An alternative embodiment,shown in dashed lines, provides an auxiliary fluid inlet 346 a connectedto the first conduit 346 with a conduit 346 b and having a control valve346 c, which may be used to flow a rinsing fluid on the backside of thesubstrate after the dissolving fluid is flown without having to reorientthe substrate or switch the flow through the second fluid inlet to arinsing fluid.

[0060] In one embodiment, the substrate is mounted with the depositionsurface of the disposed face up in the SRD module bowl. As will beexplained below, for such an arrangement, the first fluid inlet wouldgenerally flow a rinsing fluid, typically deionized water or alcohol.Consequently, the backside of the substrate would be mounted facing downand a fluid flowing through the second fluid inlet would be a dissolvingfluid, such as an acid, including hydrochloric acid, sulfuric acid,phosphoric acid, hydrofluoric acid, or other dissolving liquids orfluids, depending on the material to be dissolved. Alternatively, thefirst fluid and the second fluid are both rinsing fluids, such asdeionized water or alcohol, when the desired process is to rinse theprocessed substrate.

[0061] In operation, the pedestal is in a raised position, shown in FIG.4, and a robot (not shown) places the substrate, front side up, onto thepedestal. The pedestal lowers the substrate to a processing positionwhere the substrate is vertically disposed between the first and thesecond fluid inlets. Generally, the pedestal actuator rotates thepedestal between about 5 to about 5000 rpm, with a typical range betweenabout 20 to about 2000 rpm for a 200 mm substrate. The rotation causesthe lower end 337 a of the clamps to rotate outward about pivot 337 b,toward the periphery of the SRD module sidewall, due to centrifugalforce. The clamp rotation forces the upper end 337 c of the clamp inwardand downward to center and hold the substrate 338 in position on thepedestal 336, preferably along the substrate edge. The clamps may rotateinto position without touching the substrate and hold the substrate inposition on the pedestal only if the substrate significantly lifts offthe pedestal during processing. With the pedestal rotating thesubstrate, a rinsing fluid is delivered onto the substrate front sidethrough the first fluid inlet 340. The second fluid, such as an acid, isdelivered to the backside surface through the second fluid inlet toremove any unwanted deposits. The dissolving fluid chemically reactswith the deposited material and dissolves and then flushes the materialaway from the substrate backside and other areas where any unwanteddeposits are located. In a preferred embodiment, the rinsing fluid isadjusted to flow at a greater rate than the dissolving fluid to helpprotect the front side of the substrate from the dissolving fluid. Thefirst and second fluid inlets are located for optimal performancedepending on the size of the substrate, the respective flow rates, spraypatterns, and amount and type of deposits to be removed, among otherfactors. In some instances, the rinsing fluid could be routed to thesecond fluid inlet after a dissolving fluid has dissolved the unwanteddeposits to rinse the backside of the substrate. In other instances, anauxiliary fluid inlet connected to flow rinsing fluid on the backside ofthe substrate could be used to rinse any dissolving fluid residue fromthe backside. After rinsing the front side and/or backside of thesubstrate, the fluid(s) flow is stopped and the pedestal continues torotate, spinning the substrate, and thereby effectively drying thesurface.

[0062] The fluid(s) is generally delivered in a spray pattern, which maybe varied depending on the particular nozzle spray pattern desired andmay include a fan, jet, conical, and other patterns. One spray patternfor the first and second fluids through the respective fluid inlets,when the first fluid is a rinsing fluid, is fan pattern with a pressureof about 10 to about 15 pounds per square inch (psi) and a flow rate ofabout 1 to about 3 gallons per minute (gpm) for a 200 mm wafer.

[0063] The invention could also be used to remove the unwanted depositsalong the edge of the substrate to create an edge exclusion zone. Byadjustment of the orientation and placement of the nozzles, the flowrates of the fluids, the rotational speed of the substrate, and thechemical composition of the fluids, the unwanted deposits could beremoved from the edge and/or edge exclusion zone of the substrate aswell. Thus, substantially preventing dissolution of the depositedmaterial on the front side surface may not necessarily include the edgeor edge exclusion zone of the substrate. Also, preventing dissolution ofthe deposited material on the front side surface is intended to includeat least preventing the dissolution so that the front side with thedeposited material is not impaired beyond a commercial value.

[0064] One method of accomplishing the edge exclusion zone dissolutionprocess is to rotate the disk at a slower speed, such as about 100 toabout 1000 rpm, while dispensing the dissolving fluid on the backside ofthe substrate. The centrifugal force moves the dissolving fluid to theedge of the substrate and forms a layer of fluid around the edge due tosurface tension of the fluid, so that the dissolving fluid overlaps fromthe backside to the front side in the edge area of the substrate. Therotational speed of the substrate and the flow rate of the dissolvingfluid may be used to determine the extent of the overlap onto the frontside. For instance, a decrease in rotational speed or an increase inflow results in a less overlap of fluid to the opposing side, e.g., thefront side. Additionally, the flow rate and flow angle of the rinsingfluid delivered to the front side can be adjusted to offset the layer ofdissolving fluid onto the edge and/or frontside of the substrate. Insome instances, the dissolving fluid may be used initially without therinsing fluid to obtain the edge and/or edge exclusion zone removal,followed by the rinsing/dissolving process of the present inventiondescribed above.

[0065] The SRD module 238 is connected between the loading station 210and the mainframe 214. The mainframe 214 generally comprises a mainframetransfer station 216 and a plurality of processing stations 218.Referring to FIGS. 2 and 3, the mainframe 214, as shown, includes twoprocessing stations 218, each processing station 218 having twoprocessing cells 240. The mainframe transfer station 216 includes amainframe transfer robot 242. Preferably, the mainframe transfer robot242 comprises a plurality of individual robot arms 244 that providesindependent access of wafers in the processing stations 218 and the SRDstations 212. As shown in FIG. 3, the mainframe transfer robot 242comprises two robot arms 244, corresponding to the number of processingcells 240 per processing station 218. Each robot arm 244 includes arobot blade 246 for holding a wafer during a wafer transfer. Preferably,each robot arm 244 is operable independently of the other arm tofacilitate independent transfers of wafers in the system. Alternatively,the robot arms 244 operate in a linked fashion such that one robotextends as the other robot arm retracts.

[0066] Preferably, the mainframe transfer station 216 includes a flipperrobot 248 that facilitates transfer of a wafer from a face-up positionon the robot blade 246 of the mainframe transfer robot 242 to a facedown position for a process cell 240 that requires face-down processingof wafers. The flipper robot 248 includes a main body 250 that providesboth vertical and rotational movements with respect to a vertical axisof the main body 250 and a flipper robot arm 252 that providesrotational movement along a horizontal axis along the flipper robot arm252. Preferably, a vacuum suction gripper 254, disposed at the distalend of the flipper robot arm 252, holds the wafer as the wafer isflipped and transferred by the flipper robot 248. The flipper robot 248positions a wafer 234 into the processing cell 240 for face-downprocessing. The details of the electroplating processing cell accordingto the invention will be discussed below.

[0067]FIG. 24 is a top schematic view of a mainframe transfer robothaving a flipper robot incorporated therein. The mainframe transferrobot 216′ as shown in FIG. 24 serves to transfer wafers betweendifferent stations attached the mainframe station, including theprocessing stations and the SRD stations. The mainframe transfer robot216′ includes a plurality of robot arms 2402 (two shown), and a flipperrobot 2404 is attached as an end effector for each of the robot arms2402. Flipper robots are generally known in the art and can be attachedas end effectors for wafer handling robots, such as model RR701,available from Rorze Automation, Inc., located in Milpitas, Calif. Themain transfer robot 216′ having a flipper robot as the end effector iscapable of transferring substrates between different stations attachedto the mainframe as well as flipping the substrate being transferred tothe desired surface orientation, i.e., substrate processing surfacebeing face-down for the electroplating process. Preferably, themainframe transfer robot 216′ provides independent robot motion alongthe X-Y-Z axes by the robot arm 2402 and independent substrate flippingrotation by the flipper robot end effector 2404. By incorporating theflipper robot 2404 as the end effector of the mainframe transfer robot,the wafer transfer process is simplified because the step of passing awafer from a mainframe transfer robot to a flipper robot is eliminated.

[0068]FIG. 6 is a cross sectional view of an electroplating process cell400 according to the invention. The electroplating process cell 400 asshown in FIG. 6 is the same as the electroplating process cell 240 asshown in FIGS. 2 and 3. The processing cell 400 generally comprises ahead assembly 410, a process kit 420 and an electrolyte collector 440.Preferably, the electrolyte collector 440 is secured onto the body 442of the mainframe 214 over an opening 443 that defines the location forplacement of the process kit 420. The electrolyte collector 440 includesan inner wall 446, an outer wall 448 and a bottom 447 connecting thewalls. An electrolyte outlet 449 is disposed through the bottom 447 ofthe electrolyte collector 440 and connected to the electrolytereplenishing system 220 (shown in FIG. 2) through tubes, hoses, pipes orother fluid transfer connectors.

[0069] The head assembly 410 is mounted onto a head assembly frame 452.The head assembly frame 452 includes a mounting post 454 and acantilever arm 456. The mounting post 454 is mounted onto the body 442of the mainframe 214, and the cantilever arm 456 extends laterally froman upper portion of the mounting post 454. Preferably, the mounting post454 provides rotational movement with respect to a vertical axis alongthe mounting post to allow rotation of the head assembly 410. The headassembly 410 is attached to a mounting plate 460 disposed at the distalend of the cantilever arm 456. The lower end of the cantilever arm 456is connected to a cantilever arm actuator 457, such as a pneumaticcylinder, mounted on the mounting post 454. The cantilever arm actuator457 provides pivotal movement of the cantilever arm 456 with respect tothe joint between the cantilever arm 456 and the mounting post 454. Whenthe cantilever arm actuator 457 is retracted, the cantilever arm 456moves the head assembly 410 away from the process kit 420 to provide thespacing required to remove and/or replace the process kit 420 from theelectroplating process cell 400. When the cantilever arm actuator 457 isextended, the cantilever arm 456 moves the head assembly 410 toward theprocess kit 420 to position the wafer in the head assembly 410 in aprocessing position.

[0070] The head assembly 410 generally comprises a wafer holder assembly450 and a wafer assembly actuator 458. The wafer assembly actuator 458is mounted onto the mounting plate 460, and includes a head assemblyshaft 462 extending downwardly through the mounting plate 460. The lowerend of the head assembly shaft 462 is connected to the wafer holderassembly 450 to position the wafer holder assembly 450 in a processingposition and in a wafer loading position.

[0071] The wafer holder assembly 450 generally comprises a wafer holder464 and a cathode contact ring 466. FIG. 7 is a cross sectional view ofone embodiment of a cathode contact ring 466 of the present invention.In general, the contact ring 466 comprises an annular body having aplurality of conducting members disposed thereon. The annular body isconstructed of an insulating material to electrically isolate theplurality of conducting members. Together the body and conductingmembers form a diametrically interior substrate seating surface which,during processing, supports a substrate and provides a current thereto.

[0072] Referring now to FIG. 7 in detail, the contact ring 466 generallycomprises a plurality of conducting members 765 at least partiallydisposed within an annular insulative body 770. The insulative body 770is shown having a flange 762 and a downward sloping shoulder portion 764leading to a substrate seating surface 768 located below the flange 762such that the flange 762 and the substrate seating surface 768 lie inoffset and substantially parallel planes. Thus, the flange 762 may beunderstood to define a first plane while the substrate seating surface768 defines a second plane parallel to the first plane wherein theshoulder 764 is disposed between the two planes. However, contact ringdesign shown in FIG. 7 is intended to be merely illustrative. In anotherembodiment, the shoulder portion 764 may be of a steeper angle includinga substantially vertical angle so as to be substantially normal to boththe flange 762 and the substrate seating surface 768. Alternatively, thecontact ring 466 may be substantially planar thereby eliminating theshoulder portion 764. However, for reasons described below, a preferredembodiment comprises the shoulder portion 764 shown in FIG. 6 or somevariation thereof.

[0073] The conducting members 765 are defined by a plurality of outerelectrical contact pads 780 annularly disposed on the flange 762, aplurality of inner electrical contact pads 772 disposed on a portion ofthe substrate seating surface 768, and a plurality of embeddedconducting connectors 776 which link the pads 772, 780 to one another.The conducting members 765 are isolated from one another by theinsulative body 770 which may be made of a plastic such aspolyvinylidenefluoride (PVDF), perfluoroalkoxy resin (PFA), Teflon™, andTefzel™, or any other insulating material such as Alumina (Al₂O₃) orother ceramics. The outer contact pads 780 are coupled to a power supply(not shown) to deliver current and voltage to the inner contact pads 772via the connectors 776 during processing. In turn, the inner contactpads 772 supply the current and voltage to a substrate by maintainingcontact around a peripheral portion of the substrate. Thus, in operationthe conducting members 765 act as discrete current paths electricallyconnected to a substrate.

[0074] Low resistivity, and conversely high conductivity, are directlyrelated to good plating. To ensure low resistivity, the conductingmembers 765 are preferably made of copper (Cu), platinum (Pt), tantalum(Ta), titanium (Ti), gold (Au), silver (Ag), stainless steel or otherconducting materials. Low resistivity and low contact resistance mayalso be achieved by coating the conducting members 765 with a conductingmaterial. Thus, the conducting members 765 may, for example, be made ofcopper (resistivity for copper is approximately 2×10⁻⁸Ω·m) and be coatedwith platinum (resistivity for platinum is approximately 10.6×10⁻⁸Ω·m).Coatings such as tantalum nitride (TaN), titanium nitride (TiN), rhodium(Rh), Au, Cu, or Ag on a conductive base materials such as stainlesssteel, molybdenum (Mo), Cu, and Ti are also possible. Further, since thecontact pads 772, 780 are typically separate units bonded to theconducting connectors 776, the contact pads 772, 780 may comprise onematerial, such as Cu, and the conducting members 765 another, such asstainless steel. Either or both of the pads 772, 180 and conductingconnectors 776 may be coated with a conducting material. Additionally,because plating repeatability may be adversely affected by oxidationwhich acts as an insulator, the inner contact pads 772 preferablycomprise a material resistant to oxidation such as Pt, Ag, or Au.

[0075] In addition to being a function of the contact material, thetotal resistance of each circuit is dependent on the geometry, or shape,of the inner contact inner contact pads 772 and the force supplied bythe contact ring 466. These factors define a constriction resistance,R_(CR), at the interface of the inner contact pads 772 and the substrateseating surface 768 due to asperities between the two surfaces.Generally, as the applied force is increased the apparent area is alsoincreased. The apparent area is, in turn, inversely related to R_(CR) sothat an increase in the apparent area results in a decreased R_(CR).Thus, to minimize overall resistance it is preferable to maximize force.The maximum force applied in operation is limited by the yield strengthof a substrate which may be damaged under excessive force and resultingpressure. However, because pressure is related to both force and area,the maximum sustainable force is also dependent on the geometry of theinner contact pads 772. Thus, while the contact pads 772 may have a flatupper surface as in FIG. 7, other shapes may be used to advantage. Forexample, two preferred shapes are shown in FIGS. 8 and 9. FIG. 8 shows aknife-edge contact pad and FIG. 9 shows a hemispherical contact pad. Aperson skilled in the art will readily recognize other shapes which maybe used to advantage. A more complete discussion of the relation betweencontact geometry, force, and resistance is given in Ney Contact Manual,by Kenneth E. Pitney, The J. M. Ney Company, 1973, which is herebyincorporated by reference in its entirety.

[0076] The number of connectors 776 may be varied depending on theparticular number of contact pads 772 (shown in FIG. 7) desired. For a200 mm substrate, preferably at least twenty-four connectors 776 arespaced equally over 360°. However, as the number of connectors reaches acritical level, the compliance of the substrate relative to the contactring 466 is adversely affected. Therefore, while more than twenty-fourconnectors 776 may be used, contact uniformity may eventually diminishdepending on the topography of the contact pads 772 and the substratestiffness. Similarly, while less than twenty-four connectors 776 may beused, current flow is increasingly restricted and localized, leading topoor plating results. Since the dimensions of the present invention arereadily altered to suit a particular application (for example, a 300 mmsubstrate), the optimal number may easily be determined for varyingscales and embodiments.

[0077] As shown in FIG. 10, the substrate seating surface 768 comprisesan isolation gasket 782 disposed on the insulative body 770 andextending diametrically interior to the inner contact pads 772 to definethe inner diameter of the contact ring 466. The isolation gasket 782preferably extends slightly above the inner contact pads 772 (e.g., afew mils) and preferably comprises an elastomer such as Viton™, Teflon™,buna rubber and the like. Where the insulative body 770 also comprisesan elastomer the isolation gasket 782 may be of the same material. Inthe latter embodiment, the isolation gasket 782 and the insulative body770 may be monolithic, i.e., formed as a single piece. However, theisolation gasket 782 is preferably separate from the insulative body 770so that it may be easily removed for replacement or cleaning.

[0078] While FIG. 10 shows a preferred embodiment of the isolationgasket 782 wherein the isolation gasket is seated entirely on theinsulative body 770, FIGS. 8 and 9 show an alternative embodiment. Inthe latter embodiment, the insulative body 770 is partially machinedaway to expose the upper surface of the connecting member 776 and theisolation gasket 782 is disposed thereon. Thus, the isolation gasket 782contacts a portion of the connecting member 776. This design requiresless material to be used for the inner contact pads 772 which may beadvantageous where material costs are significant such as when the innercontact pads 772 comprise gold. Persons skilled in the art willrecognize other embodiments which do not depart from the scope of thepresent invention.

[0079] During processing, the isolation gasket 782 maintains contactwith a peripheral portion of the substrate plating surface and iscompressed to provide a seal between the remaining cathode contact ring466 and the substrate. The seal prevents the electrolyte from contactingthe edge and backside of the substrate. As noted above, maintaining aclean contact surface is necessary to achieving high platingrepeatability. Previous contact ring designs did not provide consistentplating results because contact surface topography varied over time. Thecontact ring of the present invention eliminates, or substantiallyminimizes, deposits which would otherwise accumulate on the innercontact pads 772 and change their characteristics thereby producinghighly repeatable, consistent, and uniform plating across the substrateplating surface.

[0080]FIG. 11 is a simplified schematic diagram representing a possibleconfiguration of the electrical circuit for the contact ring 466. Toprovide a uniform current distribution between the conducting members765, an external resistor 700 is connected in series with each of theconducting members 765. Preferably, the resistance value of the externalresistor 700 (represented as R_(EXT)) is much greater than theresistance of any other component of the circuit. As shown in FIG. 11,the electrical circuit through each conducting member 765 is representedby the resistance of each of the components connected in series with thepower supply 702. R_(E) represents the resistance of the electrolyte,which is typically dependent on the distance between the anode and thecathode contact ring and the composition of the electrolyte chemistry.Thus, R_(A) represents the resistance of the electrolyte adjacent thesubstrate plating surface 754. R_(S) represents the resistance of thesubstrate plating surface 754, and R_(C) represents the resistance ofthe cathode conducting members 765 plus the constriction resistanceresulting at the interface between the inner contact pads 772 and thesubstrate plating layer 754. Generally, the resistance value of theexternal resistor (R_(EXT)) is at least as much as ΣR (where ΣR equalsthe sum of R_(E), R_(A), R_(S) and R_(C)). Preferably, the resistancevalue of the external resistor (R_(EXT)) is much greater than ΣR suchthat ΣR is negligible and the resistance of each series circuitapproximates R_(EXT).

[0081] Typically, one power supply is connected to all of the outercontact pads 780 of the cathode contact ring 466, resulting in parallelcircuits through the inner contact pads 772. However, as the innercontact pad-to-substrate interface resistance varies with each innercontact pad 772, more current will flow, and thus more plating willoccur, at the site of lowest resistance. However, by placing an externalresistor in series with each conducting member 765, the value orquantity of electrical current passed through each conducting member 765becomes controlled mainly by the value of the external resistor. As aresult, the variations in the electrical properties between each of theinner contact pads 772 do not affect the current distribution on thesubstrate, and a uniform current density results across the platingsurface which contributes to a uniform plating thickness. The externalresistors also provide a uniform current distribution between differentsubstrates of a process-sequence.

[0082] Although the contact ring 466 of the present invention isdesigned to resist deposit buildup on the inner contact pads 772, overmultiple substrate plating cycles the substrate-pad interface resistancemay increase, eventually reaching an unacceptable value. An electronicsensor/alarm 704 can be connected across the external resistor 700 tomonitor the voltage/current across the external resistor to address thisproblem. If the voltage/current across the external resistor 700 fallsoutside of a preset operating range that is indicative of a highsubstrate-pad resistance, the sensor/alarm 704 triggers correctivemeasures such as shutting down the plating process until the problemsare corrected by an operator. Alternatively, a separate power supply canbe connected to each conducting member 765 and can be separatelycontrolled and monitored to provide a uniform current distributionacross the substrate. A very smart system (VSS) may also be used tomodulate the current flow. The VSS typically comprises a processing unitand any combination of devices known in the industry used to supplyand/or control current such as variable resistors, separate powersupplies, etc. As the physiochemical, and hence electrical, propertiesof the inner contact pads 772 change over time, the VSS processes andanalyzes data feedback. The data is compared to pre-establishedsetpoints and the VSS then makes appropriate current and voltagealterations to ensure uniform deposition.

[0083]FIG. 18 is a perspective view of an alternative embodiment of acathode contact ring. The cathode contact ring 1800 as shown in FIG. 18comprises a conductive metal or a metal alloy, such as stainless steel,copper, silver, gold, platinum, titanium, tantalum, and other conductivematerials, or a combination of conductive materials, such as stainlesssteel coated with platinum. The cathode contact ring 1800 includes anupper mounting portion 1810 adapted for mounting the cathode contactring onto the wafer holder assembly and a lower substrate receivingportion 1820 adapted for receiving a substrate therein. The substratereceiving portion 1820 includes an annular substrate seating surface1822 having a plurality of contact pads or bumps 1824 disposed thereonand preferably evenly spaced apart. When a substrate is positioned onthe substrate seating surface 1822, the contact pads 1824 physicallycontact a peripheral region of the substrate to provide electricalcontact to the electroplating seed layer on the substrate depositionsurface. Preferably, the contact pads 1824 are coated with a noblemetal, such as platinum or gold, that is resistant to oxidation.

[0084] The exposed surfaces of the cathode contact ring, except thesurfaces of the contact pads that come in contact with the substrate,are preferably treated to provide hydrophilic surfaces or coated with amaterial that exhibits hydrophilic properties. Hydrophilic materials andhydrophilic surface treatments are known in the art. One companyproviding a hydrophilic surface treatment is Millipore Corporation,located in Bedford, Mass. The hydrophilic surface significantly reducesbeading of the electrolyte on the surfaces of the cathode contact ringand promotes smooth dripping of the electrolyte from the cathode contactring after the cathode contact ring is removed from the electroplatingbath or electrolyte. By providing hydrophilic surfaces on the cathodecontact ring that facilitate run-off of the electrolyte, plating defectscaused by residual electrolyte on the cathode contact ring aresignificantly reduced. The inventors also contemplate application ofthis hydrophilic treatment or coating in other embodiments of cathodecontact rings to reduce residual electrolyte beading on the cathodecontact ring and the plating defects on a subsequently processedsubstrate that may result therefrom.

[0085] Referring to FIGS. 12 and 12A, the wafer holder 464 is preferablypositioned above the cathode contact ring 466 and comprises a bladderassembly 470 that provides pressure to the backside of a wafer andensures electrical contact between the wafer plating surface and thecathode contact ring 466. The inflatable bladder assembly 470 isdisposed on a wafer holder plate 832. A bladder 836 disposed on a lowersurface of the wafer holder plate 832 is thus located opposite andadjacent to the contacts on the cathode contact ring 466 with thesubstrate 821 interposed therebetween. A fluid source 838 supplies afluid, i.e., a gas or liquid, to the bladder 836 allowing the bladder836 to be inflated to varying degrees.

[0086] Referring now to FIGS. 12, 12A, and 13, the details of thebladder assembly 470 will be discussed. The wafer holder plate 832 isshown as substantially disc-shaped having an annular recess 840 formedon a lower surface and a centrally disposed vacuum port 841. One or moreinlets 842 are formed in the wafer holder plate 832 and lead into therelatively enlarged annular mounting channel 843 and the annular recess840. Quick-disconnect hoses 844 couple the fluid source 838 to theinlets 842 to provide a fluid thereto. The vacuum port 841 is preferablyattached to a vacuum/pressure pumping system 859 adapted to selectivelysupply a pressure or create a vacuum at a backside of the substrate 821.The pumping system 859, shown in FIG. 12, comprises a pump 845, across-over valve 847, and a vacuum ejector 849 (commonly known as aventuri). One vacuum ejector that may be used to advantage in thepresent invention is available from SMC Pneumatics, Inc., ofIndianapolis, Ind. The pump 845 may be a commercially availablecompressed gas source and is coupled to one end of a hose 851, the otherend of the hose 851 being coupled to the vacuum port 841. The hose 851is split into a pressure line 853 and a vacuum line 855 having thevacuum ejector 849 disposed therein. Fluid flow is controlled by thecross-over valve 847 which selectively switches communication with thepump 845 between the pressure line 853 and the vacuum line 855.Preferably, the cross-over valve has an OFF setting whereby fluid isrestricted from flowing in either direction through hose 851. A shut-offvalve 861 disposed in hose 851 prevents fluid from flowing from pressureline 855 upstream through the vacuum ejector 849. The desired directionof fluid flow is indicated by arrows.

[0087] Persons skilled in the art will readily appreciate otherarrangements which do not depart from the spirit and scope of thepresent invention. For example, where the fluid source 838 is a gassupply it may be coupled to hose 851 thereby eliminating the need for aseparate compressed gas supply, i.e., pump 845. Further, a separate gassupply and vacuum pump may supply the backside pressure and vacuumconditions. While it is preferable to allow for both a backside pressureas well as a backside vacuum, a simplified embodiment may comprise apump capable of supplying only a backside vacuum. However, as will beexplained below, deposition uniformity may be improved where a backsidepressure is provided during processing. Therefore, an arrangement suchas the one described above including a vacuum ejector and a cross-overvalve is preferred.

[0088] Referring now to FIGS. 12A and 14, a substantially circularring-shaped manifold 846 is disposed in the annular recess 840. Themanifold 846 comprises a mounting rail 852 disposed between an innershoulder 848 and an outer shoulder 850. The mounting rail 852 is adaptedto be at least partially inserted into the annular mounting channel 843.A plurality of fluid outlets 854 formed in the manifold 846 providecommunication between the inlets 842 and the bladder 836. Seals 837,such as O-rings, are disposed in the annular manifold channel 843 inalignment with the inlet 842 and outlet 854 and secured by the waferholder plate 832 to ensure an airtight seal. Conventional fasteners (notshown) such as screws may be used to secure the manifold 846 to thewafer holder plate 832 via cooperating threaded bores (not shown) formedin the manifold 846 and the wafer holder plate 832.

[0089] Referring now to FIG. 15, the bladder 836 is shown, in section,as an elongated substantially semi-tubular piece of material havingannular lip seals 856, or nodules, at each edge. In FIG. 12A, the lipseals 856 are shown disposed on the inner shoulder 848 and the outershoulder 850. A portion of the bladder 836 is compressed against thewalls of the annular recess 840 by the manifold 846 which has a widthslightly less (e.g. a few millimeters) than the annular recess 840.Thus, the manifold 846, the bladder 836, and the annular recess 840cooperate to form a fluid-tight seal. To prevent fluid loss, the bladder836 is preferably comprised of some fluid impervious material such assilicon rubber or any comparable elastomer which is chemically inertwith respect to the electrolyte and exhibits reliable elasticity. Whereneeded a compliant covering 857 may be disposed over the bladder 836, asshown in FIG. 15, and secured by means of an adhesive or thermalbonding. The covering 857 preferably comprises an elastomer such asViton™, buna rubber or the like, which may be reinforced by Kevlar™, forexample. In one embodiment, the covering 857 and the bladder 836comprise the same material. The covering 857 has particular applicationwhere the bladder 836 is liable to rupturing. Alternatively, the bladder836 thickness may simply be increased during its manufacturing to reducethe likelihood of puncture. Preferably, the exposed surface of thebladder 836 (if uncovered) and the exposed surface of the covering 857are coated or treated to provide a hydrophilic surface (as discussedabove for the surfaces of the cathode contact ring) to promote drippingand removal of the residual electrolyte after the head assembly islifted above the process cell.

[0090] The precise number of inlets 842 and outlets 854 may be variedaccording to the particular application without deviating from thepresent invention. For example, while FIG. 12 shows two inlets withcorresponding outlets, an alternative embodiment could employ a singlefluid inlet which supplies fluid to the bladder 836.

[0091] In operation, the substrate 821 is introduced into the containerbody 802 by securing it to the lower side of the wafer holder plate 832.This is accomplished by engaging the pumping system 159 to evacuate thespace between the substrate 821 and the wafer holder plate 832 via port841 thereby creating a vacuum condition. The bladder 836 is theninflated by supplying a fluid such as air or water from the fluid source838 to the inlets 842. The fluid is delivered into the bladder 836 viathe manifold outlets 854, thereby pressing the substrate 821 uniformlyagainst the contacts of the cathode contact ring 466. The electroplatingprocess is then carried out. An electrolyte is then pumped into theprocess kit 420 toward the substrate 821 to contact the exposedsubstrate plating surface 820. The power supply provides a negative biasto the substrate plating surface 820 via the cathode contact ring 466.As the electrolyte is flowed across the substrate plating surface 820,ions in the electrolytic solution are attracted to the surface 820 anddeposit on the surface 820 to form the desired film.

[0092] Because of its flexibility, the bladder 836 deforms toaccommodate the asperities of the substrate backside and contacts of thecathode contact ring 466 thereby mitigating misalignment with theconducting cathode contact ring 466. The compliant bladder 836 preventsthe electrolyte from contaminating the backside of the substrate 821 byestablishing a fluid tight seal at a perimeter portion of a backside ofthe substrate 821. Once inflated, a uniform pressure is delivereddownward toward the cathode contact ring 466 to achieve substantiallyequal force at all points where the substrate 821 and cathode contactring 466 interface. The force can be varied as a function of thepressure supplied by the fluid source 838. Further, the effectiveness ofthe bladder assembly 470 is not dependent on the configuration of thecathode contact ring 466. For example, while FIG. 12 shows a pinconfiguration having a plurality of discrete contact points, the cathodecontact ring 466 may also be a continuous surface.

[0093] Because the force delivered to the substrate 821 by the bladder836 is variable, adjustments can be made to the current flow supplied bythe contact ring 466. As described above, an oxide layer may form on thecathode contact ring 466 and act to restrict current flow. However,increasing the pressure of the bladder 836 may counteract the currentflow restriction due to oxidation. As the pressure is increased, themalleable oxide layer is compromised and superior contact between thecathode contact ring 466 and the substrate 821 results. Theeffectiveness of the bladder 836 in this capacity may be furtherimproved by altering the geometry of the cathode contact ring 466. Forexample, a knife-edge geometry is likely to penetrate the oxide layermore easily than a dull rounded edge or flat edge.

[0094] Additionally, the fluid tight seal provided by the inflatedbladder 836 allows the pump 845 to maintain a backside vacuum orpressure either selectively or continuously, before, during, and afterprocessing. Generally, however, the pump 845 is run to maintain a vacuumonly during the transfer of substrates to and from the electroplatingprocess cell 400 because it has been found that the bladder 836 iscapable of maintaining the backside vacuum condition during processingwithout continuous pumping. Thus, while inflating the bladder 836, asdescribed above, the backside vacuum condition is simultaneouslyrelieved by disengaging the pumping system 859, e.g., by selecting anOFF position on the cross-over valve 847. Disengaging the pumping system859 may be abrupt or comprise a gradual process whereby the vacuumcondition is ramped down. Ramping allows for a controlled exchangebetween the inflating bladder 836 and the simultaneously decreasingbackside vacuum condition. This exchange may be controlled manually orby computer.

[0095] As described above, continuous backside vacuum pumping while thebladder 836 is inflated is not needed and may actually cause thesubstrate 820 to buckle or warp leading to undesirable depositionresults. It may, however, be desirable to provide a backside pressure tothe substrate 820 in order to cause a “bowing” effect of the substrateto be processed. The inventors of the present invention have discoveredthat bowing results in superior deposition. Thus, pumping system 859 iscapable of selectively providing a vacuum or pressure condition to thesubstrate backside. For a 200 mm wafer a backside pressure up to 5 psiis preferable to bow the substrate. Because substrates typically exhibitsome measure of pliability, a backside pressure causes the substrate tobow or assume a convex shape relative to the upward flow of theelectrolyte. The degree of bowing is variable according to the pressuresupplied by pumping system 859.

[0096] Those skilled in the art will readily recognize other embodimentswhich are contemplated by the present invention. For example, while FIG.12A shows a preferred bladder 836 having a surface area sufficient tocover a relatively small perimeter portion of the substrate backside ata diameter substantially equal to the cathode contact ring 466, thebladder assembly 470 may be geometrically varied. Thus, the bladderassembly may be constructed using more fluid impervious material tocover an increased surface area of the substrate 821.

[0097]FIG. 19 is a partial cross sectional view of an alternativeembodiment of a wafer holder assembly. The alternative wafer holderassembly 1900 comprises a bladder assembly 470, as described above,having the inflatable bladder 836 attached to the back surface of anintermediary wafer holder plate 1910. Preferably, a portion of theinflatable bladder 836 is sealingly attached to the back surface 1912 ofthe intermediary wafer holder plate 1910 using an adhesive or otherbonding material. The front surface 1914 of the intermediary waferholder plate 1910 is adapted to receive a wafer or substrate 821 to beprocessed, and an elastomeric o-ring 1916 is disposed in an annulargroove 1918 on the front surface 1914 of the intermediary wafer holderplate 1910 to contact a peripheral portion of the wafer back surface.The elastomeric o-ring 1916 provides a seal between the wafer backsurface and the front surface of the intermediary wafer holder plate.Preferably, the intermediary wafer holder plate includes a plurality ofbores or holes 1920 extending through the plate that are in fluidcommunication with the vacuum port 841 to facilitate securing the waferon the wafer holder using a vacuum force applied to the backside of thewafer. According to this alternative embodiment of the wafer holderassembly, the inflatable bladder does not directly contact a wafer beingprocessed, and thus the risk of cutting or damaging the inflatablebladder during wafer transfers is significantly reduced. The elastomericO-ring 1916 is preferably coated or treated to provide a hydrophilicsurface (as discussed above for the surfaces of the cathode contactring) for contacting the wafer, and the elastomeric O-ring 1916 isreplaced as needed to ensure proper contact and seal to the wafer.

[0098]FIG. 25 is an alternative embodiment of the process head assemblyhaving a rotatable head assembly 2410. Preferably, a rotational actuatoris disposed on the cantilevered arm and attached to the head assembly torotate the head assembly during wafer processing. The rotatable headassembly 2410 is mounted onto a head assembly frame 2452. Thealternative head assembly frame 2452 and the rotatable head assembly2410 are mounted onto the mainframe similarly to the head assembly frame452 and head assembly 410 as shown in FIG. 6 and described above. Thehead assembly frame 2452 includes a mounting post 2454, a post cover2455, and a cantilever arm 2456. The mounting post 2454 is mounted ontothe body of the mainframe 214, and the post cover 2455 covers a topportion of the mounting post 2454. Preferably, the mounting post 454provides rotational movement (as indicated by arrow A1) with respect toa vertical axis along the mounting post to allow rotation of the headassembly frame 2452. The cantilever arm 2456 extends laterally from anupper portion of the mounting post 2454 and is pivotally connected tothe post cover 2455 at the pivot joint 2459. The rotatable head assembly2410 is attached to a mounting slide 2460 disposed at the distal end ofthe cantilever arm 2456. The mounting slide 2460 guides the verticalmotion of the head assembly 2410. A head lift actuator 2458 is disposedon top of the mounting slide 2460 to provide vertical displacement ofthe head assembly 2410.

[0099] The lower end of the cantilever arm 2456 is connected to theshaft 2453 of a cantilever arm actuator 2457, such as a pneumaticcylinder or a lead-screw actuator, mounted on the mounting post 2454.The cantilever arm actuator 2457 provides pivotal movement (as indicatedby arrow A2) of the cantilever arm 2456 with respect to the joint 2459between the cantilever arm 2456 and the post cover 2454. When thecantilever arm actuator 2457 is retracted, the cantilever arm 2456 movesthe head assembly 2410 away from the process kit 420 to provide thespacing required to remove and/or replace the process kit 420 from theelectroplating process cell 240. When the cantilever arm actuator 2457is extended, the cantilever arm 2456 moves the head assembly 2410 towardthe process kit 420 to position the wafer in the head assembly 2410 in aprocessing position.

[0100] The rotatable head assembly 2410 includes a rotating actuator2464 slideably connected to the mounting slide 2460. The shaft 2468 ofthe head lift actuator 2458 is inserted through a lift guide 2466attached to the body of the rotating actuator 2464. Preferably, theshaft 2468 is a lead-screw type shaft that moves the lift guide (asindicated by arrows A3) between various vertical position. The rotatingactuator 2464 is connected to the wafer holder assembly 2450 through theshaft 2470 and rotates the wafer holder assembly 2450 (as indicated byarrows A4). The wafer holder assembly 2450 includes a bladder assembly,such as the embodiments described above with respect to FIGS. 12-15 and19, and a cathode contact ring, such as the embodiments described abovewith respect to FIGS. 7-10 and 18.

[0101] The rotation of the wafer during the electroplating processgenerally enhances the deposition results. Preferably, the head assemblyis rotated between about 2 rpm and about 20 rpm during theelectroplating process. The head assembly can also be rotated as thehead assembly is lowered to position the wafer in contact with theelectrolyte in the process cell as well as when the head assembly israised to remove the wafer from the electrolyte in the process cell. Thehead assembly is preferably rotated at a high speed (i.e., >20 rpm)after the head assembly is lifted from the process cell to enhanceremoval of residual electrolyte on the head assembly.

[0102] In one embodiment, the inventors have improved the uniformity ofthe deposited film to within about 2% (i.e., maximum deviation ofdeposited film thickness is at about 2% of the average film thickness)while standard electroplating processes typically achieves uniformity atbest within about 5.5%. However, rotation of the head assembly is notnecessary to achieve uniform electroplating deposition in someinstances, particularly where the uniformity of electroplatingdeposition is achieved by adjusting the processing parameters, such asthe electrolyte chemistry, electrolyte flow and other parameters.

[0103] Referring back to FIG. 6, a cross sectional view of anelectroplating process cell 400, the wafer holder assembly 450 ispositioned above the process kit 420. The process kit 420 generallycomprises a bowl 430, a container body 472, an anode assembly 474 and afilter 476. Preferably, the anode assembly 474 is disposed below thecontainer body 472 and attached to a lower portion of the container body472, and the filter 476 is disposed between the anode assembly 474 andthe container body 472. The container body 472 is preferably acylindrical body comprised of an electrically insulative material, suchas ceramics, plastics, plexiglass (acrylic), lexane, PVC, CPVC, andPVDF. Alternatively, the container body 472 can be made from a metal,such as stainless steel, nickel and titanium, which is coated with aninsulating layer, such as Teflon™, PVDF, plastic, rubber and othercombinations of materials that do not dissolve in the electrolyte andcan be electrically insulated from the electrodes (i.e., the anode andcathode of the electroplating system). The container body 472 ispreferably sized and adapted to conform to the wafer plating surface andthe shape of the of a wafer being processed through the system,typically circular or rectangular in shape. One preferred embodiment ofthe container body 472 comprises a cylindrical ceramic tube having aninner diameter that has about the same dimension as or slightly largerthan the wafer diameter. The inventors have discovered that therotational movement typically required in typical electroplating systemsis not required to achieve uniform plating results when the size of thecontainer body conforms to about the size of the wafer plating surface.

[0104] An upper portion of the container body 472 extends radiallyoutwardly to form an annular weir 478. The weir 478 extends over theinner wall 446 of the electrolyte collector 440 and allows theelectrolyte to flow into the electrolyte collector 440. The uppersurface of the weir 478 preferably matches the lower surface of thecathode contact ring 466. Preferably, the upper surface of the weir 478includes an inner annular flat portion 480, a middle inclined portion482 and an outer declined portion 484. When a wafer is positioned in theprocessing position, the wafer plating surface is positioned above thecylindrical opening of the container body 472, and a gap for electrolyteflow is formed between the lower surface of the cathode contact ring 466and the upper surface of the weir 478. The lower surface of the cathodecontact ring 466 is disposed above the inner flat portion 480 and themiddle inclined portion of the weir 478. The outer declined portion 484is sloped downwardly to facilitate flow of the electrolyte into theelectrolyte collector 440.

[0105] A lower portion of the container body 472 extends radiallyoutwardly to form a lower annular flange 486 for securing the containerbody 472 to the bowl 430. The outer dimension (i.e., circumference) ofthe annular flange 486 is smaller than the dimensions of the opening 444and the inner circumference of the electrolyte collector 440 to allowremoval and replacement of the process kit 420 from the electroplatingprocess cell 400. Preferably, a plurality of bolts 488 are fixedlydisposed on the annular flange 486 and extend downwardly throughmatching bolt holes on the bowl 430. A plurality of removable fastenernuts 490 secure the process kit 420 onto the bowl 430. A seal 487, suchas an elastomer O-ring, is disposed between container body 472 and thebowl 430 radially inwardly from the bolts 488 to prevent leaks from theprocess kit 420. The nuts/bolts combination facilitates fast and easyremoval and replacement of the components of the process kit 420 duringmaintenance.

[0106] Preferably, the filter 476 is attached to and completely coversthe lower opening of the container body 472, and the anode assembly 474is disposed below the filter 476. A spacer 492 is disposed between thefilter 476 and the anode assembly 474. Preferably, the filter 476, thespacer 492, and the anode assembly 474 are fastened to a lower surfaceof the container body 472 using removable fasteners, such as screwsand/or bolts. Alternatively, the filter 476, the spacer 492, and theanode assembly 474 are removably secured to the bowl 430.

[0107] The anode assembly 474 preferably comprises a consumable anodethat serves as a metal source in the electrolyte. Alternatively, theanode assembly 474 comprises a non-consumable anode, and the metal to beelectroplated is supplied within the electrolyte from the electrolytereplenishing system 220. As shown in FIG. 6, the anode assembly 474 is aself-enclosed module having a porous anode enclosure 494 preferably madeof the same metal as the metal to be electroplated, such as copper.Alternatively, the anode enclosure 494 is made of porous materials, suchas ceramics or polymeric membranes. A soluble metal 496, such as highpurity copper for electro-chemical deposition of copper, is disposedwithin the anode enclosure 494. The soluble metal 496 preferablycomprises metal particles, wires or a perforated sheet. The porous anodeenclosure 494 also acts as a filter that keeps the particulatesgenerated by the dissolving metal within the anode enclosure 494. Ascompared to a non-consumable anode, the consumable (i.e., soluble) anodeprovides gas-generation-free electrolyte and minimizes the need toconstantly replenish the metal in the electrolyte.

[0108] An anode electrode contact 498 is inserted through the anodeenclosure 494 to provide electrical connection to the soluble metal 496from a power supply. Preferably, the anode electrode contact 498 is madefrom a conductive material that is insoluble in the electrolyte, such astitanium, platinum and platinum-coated stainless steel. The anodeelectrode contact 498 extends through the bowl 430′ and is connected toan electrical power supply. Preferably, the anode electrical contact 498includes a threaded portion 497 for a fastener nut 499 to secure theanode electrical contact 498 to the bowl 430, and a seal 495, such as aelastomer washer, is disposed between the fastener nut 499 and the bowl430 to prevent leaks from the process kit 420.

[0109] The bowl 430 generally comprises a cylindrical portion 502 and abottom portion 504. An upper annular flange 506 extends radiallyoutwardly from the top of the cylindrical portion 502. The upper annularflange 506 includes a plurality of holes 508 that matches the number ofbolts 488 from the lower annular flange 486 of the container body 472.To secure the upper annular flange 506 of the bowl 430 and the lowerannular flange 486 of the container body 472, the bolts 488 are insertedthrough the holes 508, and the fastener nuts 490 are fastened onto thebolts 488. Preferably, the outer dimension (i.e., circumference) of theupper annular flange 506 is about the same as the outer dimension (i.e.,circumference) of the lower annular flange 486. Preferably, the lowersurface of the upper annular flange 506 of the bowl 430 rests on asupport flange of the mainframe 214 when the process kit 420 ispositioned on the mainframe 214.

[0110] The inner circumference of the cylindrical portion 502accommodates the anode assembly 474 and the filter 476. Preferably, theouter dimensions of the filter 476 and the anode assembly 474 areslightly smaller than the inner dimension of the cylindrical portion 502to force a substantial portion of the electrolyte to flow through theanode assembly 474 first before flowing through the filter 476. Thebottom portion 504 of the bowl 430 includes an electrolyte inlet 510that connects to an electrolyte supply line from the electrolytereplenishing system 220. Preferably, the anode assembly 474 is disposedabout a middle portion of the cylindrical portion 502 of the bowl 430 toprovide a gap for electrolyte flow between the anode assembly 474 andthe electrolyte inlet 510 on the bottom portion 504.

[0111] The electrolyte inlet 510 and the electrolyte supply line arepreferably connected by a releasable connector that facilitates easyremoval and replacement of the process kit 420. When the process kit 420needs maintenance, the electrolyte is drained from the process kit 420,and the electrolyte flow in the electrolyte supply line is discontinuedand drained. The connector for the electrolyte supply line is releasedfrom the electrolyte inlet 510, and the electrical connection to theanode assembly 474 is also disconnected. The head assembly 410 is raisedor rotated to provide clearance for removal of the process kit 420. Theprocess kit 420 is then removed from the mainframe 214, and a new orreconditioned process kit is replaced into the mainframe 214.

[0112] Alternatively, the bowl 430 can be secured onto the supportflange of the mainframe 214, and the container body 472 along with theanode and the filter are removed for maintenance. In this case, the nutssecuring the anode assembly 474 and the container body 472 to the bowl430 are removed to facilitate removal of the anode assembly 474 and thecontainer body 472. New or reconditioned anode assembly 474 andcontainer body 472 are then replaced into the mainframe 214 and securedto the bowl 430.

[0113]FIG. 20 is a cross sectional view of a first embodiment of anencapsulated anode. The encapsulated anode 2000 includes a permeableanode enclosure that filters or traps “anode sludge” or particulatesgenerated as the metal is dissolved from the anode plate 2004. As shownin FIG. 20, the consumable anode plate 2004 comprises a solid piece ofcopper, preferably, high purity, oxygen free copper, enclosed in ahydrophilic anode encapsulation membrane 2002. The anode plate 2004 issecured and supported by a plurality of electrical contacts orfeed-throughs 2006 that extend through the bottom of the bowl 430. Theelectrical contacts or feed-throughs 2006 extend through the anodeencapsulation membrane 2002 into the bottom surface of the anode plate2004. The flow of the electrolyte is indicated by the arrows A from theelectrolyte inlet 510 disposed at the bottom of the bowl 430 through thegap between the anode and the bowl sidewall. The electrolyte also flowsthrough the anode encapsulation membrane 2002 by permeation into and outof the gap between the anode encapsulation membrane and the anode plate,as indicated by the arrows B. Preferably, the anode encapsulationmembrane 2002 comprises a hydrophilic porous membrane, such as amodified polyvinyllidene fluoride membrane, having porosity betweenabout 60% and 80%, more preferably about 70%, and pore sizes betweenabout 0.025 μm and about 1 μm, more preferably between about 0.1 μm andabout 0.2 μm. One example of a hydrophilic porous membrane is theDurapore Hydrophilic Membrane, available from Millipore Corporation,located in Bedford, Mass. As the electrolyte flows through theencapsulation membrane, anode sludge and particulates generated by thedissolving anode are filtered or trapped by the encapsulation membrane.Thus, the encapsulation membranes improve the purity of the electrolyteduring the electroplating process, and defect formations on thesubstrate during the electroplating process caused by anode sludge andcontaminant particulates are significantly reduced.

[0114]FIG. 21 is a cross sectional view of a second embodiment of anencapsulated anode. Similar to the first embodiment of an encapsulatedanode, the anode plate 2004 is secured and supported on the electricalfeed-throughs 2006. A top encapsulation membrane 2008 and a bottomencapsulation membrane 2010, disposed respectively above and below theanode plate 2004, are attached to a membrane support ring 2012 that isdisposed around the anode plate 2004. The top and bottom encapsulationmembranes 2008, 2010 comprise a material from the list above forencapsulation membrane of the first embodiment of the encapsulatedanode. The membrane support ring 2012 preferably comprises a relativelyrigid material (as compared to the encapsulation membrane), such asplastic or other polymers. A bypass fluid inlet 2014 is disposed throughthe bottom of the bowl 430 and through the bottom encapsulation membrane2010 to introduce electrolyte into the gap between the encapsulationmembranes and the anode plate. A bypass outlet 2016 is connected to themembrane support ring 2012 and extends through the bowl 430 tofacilitate flow of excess electrolyte with the anode sludge or generatedparticulates out of the encapsulated anode into a waste drain (notshown).

[0115] Preferably, the flow of the electrolyte within the bypass fluidinlet 2014 and the main electrolyte inlet 510 are individuallycontrolled by flow control valves 2020, 2022, respectively placed alongthe fluid lines connected to the inlets, and the fluid pressure in thebypass fluid inlet 2014 is preferably maintained at a higher pressurethan the pressure in the main electrolyte inlet 510. The flow of theelectrolyte inside the bowl 430 from the main electrolyte inlet 510 isindicated by arrows A, and the flow of the electrolyte inside theencapsulated anode 2000 is indicated by the arrows B. A portion of theelectrolyte introduced into the encapsulated anode flows out of theencapsulated anode through the bypass outlet 2016. By providing adedicated bypass electrolyte supply into the encapsulated anode, theanode sludge or particulates generated from the dissolving consumableanode is continually removed from the anode, thereby improving thepurity of the electrolyte during the electroplating process.

[0116]FIG. 22 is a cross sectional view of a third embodiment of anencapsulated anode. The third embodiment of an encapsulated anode 2000includes an anode plate 2004 secured and supported on a plurality ofelectrical feed-throughs 2006, a top and a bottom encapsulation membrane2008, 2010 attached to a membrane support ring 2012, and a bypass outlet2016 connected to the membrane support ring 2012 and extending throughthe bowl 430. This third embodiment of an encapsulated anode preferablycomprises materials as described above for the first and secondembodiments of an encapsulated anode. The bottom encapsulation membrane2010 according to the third embodiment includes one or more openings2024 disposed substantially above the main electrolyte inlet 510. Theopening 2024 is adapted to receive flow of electrolyte from the mainelectrolyte inlet 510 and is preferably about the same size as theinternal circumference of the main electrolyte inlet 510. The flow ofthe electrolyte from the main electrolyte inlet 510 is indicated by thearrows A and the flow of the electrolyte within the encapsulated anodeis indicated by the arrows B. A portion of the electrolyte flows out ofthe encapsulated anode through the bypass outlet 2016, carrying aportion of the anode sludge and particulates generated from anodedissolution.

[0117]FIG. 23 is a cross sectional view of a fourth embodiment of anencapsulated anode. The fourth embodiment of an encapsulated anode 2000includes an anode plate 2002 secured and supported on a plurality ofelectrical feed-throughs 2006, a top and a bottom encapsulation membrane2008, 2010 attached to a membrane support ring 2012, and a bypass fluidinlet 2014 disposed through the bottom of the bowl 430 and through thebottom encapsulation membrane 2010 to introduce electrolyte into the gapbetween the encapsulation membranes and the anode plate. This fourthembodiment of an encapsulated anode preferably comprises materials asdescribed above for the first and second embodiments of an encapsulatedanode. Preferably, the flow of the electrolyte through the bypass fluidinlet 2014 and the main electrolyte inlet 510 are individuallycontrolled by control valves 2020, 2022, respectively. The flow of theelectrolyte from the main electrolyte inlet 510 is indicated by thearrows A while the flow of the electrolyte through the encapsulatedanode is indicated by arrows B. For this embodiment, the anode sludgeand particulates generated by the dissolving anode plate are filteredand trapped by the encapsulation membranes as the electrolyte passesthrough the membrane.

[0118]FIG. 16 is a schematic diagram of an electrolyte replenishingsystem 220. The electrolyte replenishing system 220 provides theelectrolyte to the electroplating process cells for the electroplatingprocess. The electrolyte replenishing system 220 generally comprises amain electrolyte tank 602, a dosing module 603, a filtration module 605,a chemical analyzer module 616, and an electrolyte waste disposal system622 connected to the analyzing module 616 by an electrolyte waste drain620. One or more controllers control the composition of the electrolytein the main tank 602 and the operation of the electrolyte replenishingsystem 220. Preferably, the controllers are independently operable butintegrated with the control system 222 of the electroplating systemplatform 200.

[0119] The main electrolyte tank 602 provides a reservoir forelectrolyte and includes an electrolyte supply line 612 that isconnected to each of the electroplating process cells through one ormore fluid pumps 608 and valves 607. A heat exchanger 624 or aheater/chiller disposed in thermal connection with the main tank 602controls the temperature of the electrolyte stored in the main tank 602.The heat exchanger 624 is connected to and operated by the controller610.

[0120] The dosing module 603 is connected to the main tank 602 by asupply line and includes a plurality of source tanks 606, or feedbottles, a plurality of valves 609, and a controller 611. The sourcetanks 606 contain the chemicals needed for composing the electrolyte andtypically include a deionized water source tank and copper sulfate(CuSO₄) source tank for composing the electrolyte. Other source tanks606 may contain hydrogen sulfate (H₂SO₄), hydrogen chloride (HCl) andvarious additives such as glycol. Each source tank is preferably colorcoded and fitted with a unique mating outlet connector adapted toconnect to a matching inlet connector in the dosing module. By colorcoding the source tanks and fitting the source tanks with uniqueconnectors, errors caused by human operators when exchanging orreplacing the source tanks are significantly reduced.

[0121] The deionized water source tank preferably also providesdeionized water to the system for cleaning the system duringmaintenance. The valves 609 associated with each source tank 606regulate the flow of chemicals to the main tank 602 and may be any ofnumerous commercially available valves such as butterfly valves,throttle valves and the like. Activation of the valves 609 isaccomplished by the controller 611 which is preferably connected to thesystem control 222 to receive signals therefrom.

[0122] The electrolyte filtration module 605 includes a plurality offilter tanks 604. An electrolyte return line 614 is connected betweeneach of the process cells and one or more filter tanks 604. The filtertanks 604 remove the undesired contents in the used electrolyte beforereturning the electrolyte to the main tank 602 for re-use. The main tank602 is also connected to the filter tanks 604 to facilitatere-circulation and filtration of the electrolyte in the main tank 602.By re-circulating the electrolyte from the main tank 602 through thefilter tanks 604, the undesired contents in the electrolyte arecontinuously removed by the filter tanks 604 to maintain a consistentlevel of purity. Additionally, re-circulating the electrolyte betweenthe main tank 602 and the filtration module 605 allows the variouschemicals in the electrolyte to be thoroughly mixed.

[0123] The electrolyte replenishing system 220 also includes a chemicalanalyzer module 616 that provides real-time chemical analysis of thechemical composition of the electrolyte. The analyzer module 616 isfluidly coupled to the main tank 602 by a sample line 613 and to thewaste disposal system 622 by an outlet line 621. The analyzer module 616generally comprises at least one analyzer and a controller to operatethe analyzer. The number of analyzers required for a particularprocessing tool depends on the composition of the electrolyte. Forexample, while a first analyzer may be used to monitor theconcentrations of organic substances, a second analyzer is needed forinorganic chemicals. In the specific embodiment shown in FIG. 16 thechemical analyzer module 616 comprises an auto titration analyzer 615and a cyclic voltametric stripper (CVS) 617. Both analyzers arecommercially available from various suppliers. An auto titrationanalyzer which may be used to advantage is available from Parker Systemsand a cyclic voltametric stripper is available from ECI. The autotitration analyzer 615 determines the concentrations of inorganicsubstances such as copper chloride and acid. The CVS 617 determines theconcentrations of organic substances such as the various additives whichmay be used in the electrolyte and by-products resulting from theprocessing which are returned to the main tank 602 from the processcells.

[0124] The analyzer module shown FIG. 16 is merely illustrative. Inanother embodiment each analyzer may be coupled to the main electrolytetank by a separate supply line and be operated by separate controllers.Persons skilled in the art will recognize other embodiments.

[0125] In operation, a sample of electrolyte is flowed to the analyzermodule 616 via the sample line 613. Although the sample may be takenperiodically, preferably a continuous flow of electrolyte is maintainedto the analyzer module 616. A portion of the sample is delivered to theauto titration analyzer 615 and a portion is delivered to the CVS 617for the appropriate analysis. The controller 619 initiates commandsignals to operate the analyzers 615, 617 in order to generate data. Theinformation from the chemical analyzers 615, 617 is then communicated tothe control system 222. The control system 222 processes the informationand transmits signals which include user-defined chemical dosageparameters to the dosing controller 611. The received information isused to provide real-time adjustments to the source chemicalreplenishment rates by operating one or more of the valves 609 therebymaintaining a desired, and preferably constant, chemical composition ofthe electrolyte throughout the electroplating process. The wasteelectrolyte from the analyzer module is then flowed to the wastedisposal system 622 via the outlet line 621.

[0126] Although a preferred embodiment utilizes real-time monitoring andadjustments of the electrolyte, various alternatives may be employedaccording to the present invention. For example, the dosing module 603may be controlled manually by an operator observing the output valuesprovided by the chemical analyzer module 616. Preferably, the systemsoftware allows for both an automatic real-time adjustment mode as wellas an operator (manual) mode. Further, although multiple controllers areshown in FIG. 16, a single controller may be used to operate variouscomponents of the system such as the chemical analyzer module 616, thedosing module 603, and the heat exchanger 624. Other embodiments will beapparent to those skilled in the art.

[0127] The electrolyte replenishing system 220 also includes anelectrolyte waste drain 620 connected to an electrolyte waste disposalsystem 622 for safe disposal of used electrolytes, chemicals and otherfluids used in the electroplating system. Preferably, the electroplatingcells include a direct line connection to the electrolyte waste drain620 or the electrolyte waste disposal system 622 to drain theelectroplating cells without returning the electrolyte through theelectrolyte replenishing system 220. The electrolyte replenishing system220 preferably also includes a bleed off connection to bleed off excesselectrolyte to the electrolyte waste drain 620.

[0128] Preferably, the electrolyte replenishing system 220 also includesone or more degasser modules 630 adapted to remove undesirable gasesfrom, the electrolyte. The degasser module generally comprises amembrane that separates gases from the fluid passing through thedegasser module and a vacuum system for removing the released gases. Thedegasser modules 630 are preferably placed in line on the electrolytesupply line 612 adjacent to the process cells 240. The degasser modules630 are preferably positioned as close as possible to the process cells240 so that most of the gases from the electrolyte replenishing systemare removed by the degasser modules before the electrolyte enters theprocess cells. Preferably, each degasser module 630 includes two outletsto supply degassed electrolyte to the two process cells 240 of eachprocessing station 218. Alternatively, a degasser module 630 is providedfor each process cell. The degasser modules can be placed at many otheralternative positions. For example, the degasser module can be placed atother positions in the electrolyte replenishing system, such as alongwith the filter section or in a closed-loop system with the main tank orwith the processing cell. As another example, one degasser module isplaced in line with the electrolyte supply line 612 to provide degassedelectrolyte to all of the process cells 240 of the electro-chemicaldeposition system. Additionally, a separate degasser module ispositioned in-line or in a closed-loop with the deionized water supplyline and is dedicated for removing oxygen from the deionized watersource. Because deionized water is used to rinse the processedsubstrates, free oxygen gases are preferable removed from the deionizedwater before reaching the SRD modules so that the electroplated copperis less likely to become oxidized by the rinsing process. Degassermodules are well known in the art and commercial embodiments aregenerally available and adaptable for use in a variety of applications.A commercially available degasser module is available from MilliporeCorporation, located in Bedford, Mass.

[0129] One embodiment of the degasser module 630, as shown in FIG. 26a,includes a hydrophobic membrane 632 having a fluid (i.e., electrolyte)passage 634 on one side of the membrane 632 and a vacuum system 636disposed on the opposite side of the membrane. The enclosure 638 of thedegasser module includes an inlet 640 and one or more outlets 642. Asthe electrolyte passes through the degasser module 630, the gases andother micro-bubbles in the electrolyte are separated from theelectrolyte through the hydrophobic membrane and removed by the vacuumsystem. Another embodiment of the degasser module 630′, as shown in FIG.26b, includes a tube of hydrophobic membrane 632′ and a vacuum system636 disposed around the tube of hydrophobic membrane 632′. Theelectrolyte is introduced inside the tube of hydrophobic membrane, andas the electrolyte passes through the fluid passage 634 in the tube,gases and other micro-bubbles in the electrolyte are separated from theelectrolyte through the tube of hydrophobic membrane 632′ and removed bythe vacuum system 636 surrounding the tube. More complex designs ofdegasser modules are contemplated by the invention, including designshaving serpentine paths of the electrolyte across the membrane and othermulti-sectioned designs of degasser modules.

[0130] Although not shown in FIG. 16, the electrolyte replenishingsystem 220 may include a number of other components. For example, theelectrolyte replenishing system 220 preferably also includes one or moreadditional tanks for storage of chemicals for a wafer cleaning system,such as the SRD station. Double-contained piping for hazardous materialconnections may also be employed to provide safe transport of thechemicals throughout the system. Optionally, the electrolytereplenishing system 220 includes connections to additional or externalelectrolyte processing system to provide additional electrolyte suppliesto the electroplating system.

[0131]FIG. 17 is a cross sectional view of a rapid thermal annealchamber according to the invention. The rapid thermal anneal (RTA)chamber 211 is preferably connected to the loading station 210, andsubstrates are transferred into and out of the RTA chamber 211 by theloading station transfer robot 228. The electroplating system, as shownin FIGS. 2 and 3, preferably comprises two RTA chambers 211 disposed onopposing sides of the loading station 210, corresponding to thesymmetric design of the loading station 210. Thermal anneal processchambers are generally well known in the art, and rapid thermal annealchambers are typically utilized in substrate processing systems toenhance the properties of the deposited materials. The inventioncontemplates utilizing a variety of thermal anneal chamber designs,including hot plate designs and heat lamp designs, to enhance theelectroplating results. One particular thermal anneal chamber useful forthe present invention is the WxZ chamber available from Appliedmaterials, Inc., located in Santa Clara, Calif. Although the inventionis described using a hot plate rapid thermal anneal chamber, theinvention contemplates application of other thermal anneal chambers aswell.

[0132] The RTA chamber 211 generally comprises an enclosure 902, aheater plate 904, a heater 907 and a plurality of substrate support pins906. The enclosure 902 includes a base 908, a sidewall 910 and a top912. Preferably, a cold plate 913 is disposed below the top 912 of theenclosure. Alternatively, the cold plate is integrally formed as part ofthe top 912 of the enclosure. Preferably, a reflector insulator dish 914is disposed inside the enclosure 902 on the base 908. The reflectorinsulator dish 914 is typically made from a material such as quartz,alumina, or other material that can withstand high temperatures (i.e.,greater than about 500° C.), and act as a thermal insulator between theheater 907 and the enclosure 902. The dish 914 may also be coated with areflective material, such as gold, to direct heat back to the heaterplate 906.

[0133] The heater plate 904 preferably has a large mass compared to thesubstrate being processed in the system and is preferably fabricatedfrom a material such as silicon carbide, quartz, or other materials thatdo not react with any ambient gases in the RTA chamber 211 or with thesubstrate material. The heater 907 typically comprises a resistiveheating element or a conductive/radiant heat source and is disposedbetween the heated plate 906 and the reflector insulator dish 914. Theheater 907 is connected to a power source 916 which supplies the energyneeded to heat the heater 907. Preferably, a thermocouple 920 isdisposed in a conduit 922, disposed through the base 908 and dish 914,and extends into the heater plate 904. The thermocouple 920 is connectedto a controller (i.e., the system controller described below) andsupplies temperature measurements to the controller. The controller thenincreases or decreases the heat supplied by the heater 907 according tothe temperature measurements and the desired anneal temperature.

[0134] The enclosure 902 preferably includes a cooling member 918disposed outside of the enclosure 902 in thermal contact with thesidewall 910 to cool the enclosure 902. Alternatively, one or morecooling channels (not shown) are formed within the sidewall 910 tocontrol the temperature of the enclosure 902. The cold plate 913disposed on the inside surface of the top 912 cools a substrate that ispositioned in close proximity to the cold plate 913.

[0135] The RTA chamber 211 includes a slit valve 922 disposed on thesidewall 910 of the enclosure 902 for facilitating transfers ofsubstrates into and out of the RTA chamber. The slit valve 922selectively seals an opening 924 on the sidewall 910 of the enclosurethat communicates with the loading station 210. The loading stationtransfer robot 228 (see FIG. 2) transfers substrates into and out of theRTA chamber through the opening 924.

[0136] The substrate support pins 906 preferably comprise distallytapered members constructed from quartz, aluminum oxide, siliconcarbide, or other high temperature resistant materials. Each substratesupport pin 906 is disposed within a tubular conduit 926, preferablymade of a heat and oxidation resistant material, that extends throughthe heater plate 904. The substrate support pins 906 are connected to alift plate 928 for moving the substrate support pins 906 in a uniformmanner. The lift plate 928 is attached to an to an actuator 930, such asa stepper motor, through a lift shaft 932 that moves the lift plate 928to facilitate positioning of a substrate at various vertical positionswithin the RTA chamber. The lift shaft 932 extends through the base 908of the enclosure 902 and is sealed by a sealing flange 934 disposedaround the shaft.

[0137] To transfer a substrate into the RTA chamber 211, the slit valve922 is opened, and the loading station transfer robot 228 extends itsrobot blade having a substrate positioned thereon through the opening924 into the RTA chamber. The robot blade of the loading stationtransfer robot 228 positions the substrate in the RTA chamber above theheater plate 904, and the substrate support pins 906 are extendedupwards to lift the substrate above the robot blade. The robot bladethen retracts out of the RTA chamber, and the slit valve 922 closes theopening. The substrate support pins 906 are then retracted to lower thesubstrate to a desired distance from the heater plate 904. Optionally,the substrate support pins 906 may retract fully to place the substratein direct contact with the heater plate.

[0138] Preferably, a gas inlet 936 is disposed through the sidewall 910of the enclosure 902 to allow selected gas flow into the RTA chamber 211during the anneal treatment process. The gas inlet 936 is connected to agas source 938 through a valve 940 for controlling the flow of the gasinto the RTA chamber 211. A gas outlet 942 is preferably disposed at alower portion of the sidewall 910 of the enclosure 902 to exhaust thegases in the RTA chamber and is preferably connected to a relief/checkvalve 944 to prevent backstreaming of atmosphere from outside of thechamber. Optionally, the gas outlet 942 is connected to a vacuum pump(not shown) to exhaust the RTA chamber to a desired vacuum level duringan anneal treatment.

[0139] According to the invention, a substrate is annealed in the RTAchamber 211 after the substrate has been electroplated in theelectroplating cell and cleaned in the SRD station. Preferably, the RTAchamber 211 is maintained at about atmospheric pressure, and the oxygencontent inside the RTA chamber 211 is controlled to less than about 100ppm during the anneal treatment process. Preferably, the ambientenvironment inside the RTA chamber 211 comprises nitrogen (N₂) or acombination of nitrogen (N₂) and less than about 4% hydrogen (H₂), andthe ambient gas flow into the RTA chamber 211 is maintained at greaterthan 20 liters/min to control the oxygen content to less than 100 ppm.The electroplated substrate is preferably annealed at a temperaturebetween about 200° C. and about 450° C. for between about 30 seconds and30 minutes, and more preferably, between about 250° C. and about 400° C.for between about 1 minute and 5 minutes. Rapid thermal annealprocessing typically requires a temperature increase of at least 50° C.per second. To provide the required rate of temperature increase for thesubstrate during the anneal treatment, the heater plate is preferablymaintained at between about 350° C. and about 450° C, and the substrateis preferably positioned at between about 0 mm (i.e., contacting theheater plate) and about 20 mm from the heater plate for the duration ofthe anneal treatment process. Preferably, a control system 222 controlsthe operation of the RTA chamber 211, including maintaining the desiredambient environment in the RTA chamber and the temperature of the heaterplate.

[0140] After the anneal treatment process is completed, the substratesupport pins 906 lift the substrate to a position for transfer out ofthe RTA chamber 211. The slit valve 922 opens, and the robot blade ofthe loading station transfer robot 228 is extended into the RTA chamberand positioned below the substrate. The substrate support pins 906retract to lower the substrate onto the robot blade, and the robot bladethen retracts out of the RTA chamber. The loading station transfer robot228 then transfers the processed substrate into the cassette 232 forremoval out of the electroplating processing system. (see FIGS. 2 and3).

[0141] Referring back to FIG. 2, the electroplating system platform 200includes a control system 222 that controls the functions of eachcomponent of the platform. Preferably, the control system 222 is mountedabove the mainframe 214 and comprises a programmable microprocessor. Theprogrammable microprocessor is typically programmed using a softwaredesigned specifically for controlling all components of theelectroplating system platform 200. The control system 222 also provideselectrical power to the components of the system and includes a controlpanel 223 that allows an operator to monitor and operate theelectroplating system platform 200. The control panel 223, as shown inFIG. 2, is a stand-alone module that is connected to the control system222 through a cable and provides easy access to an operator. Generally,the control system 222 coordinates the operations of the loading station210, the RTA chamber 211, the SRD station 212, the mainframe 214 and theprocessing stations 218. Additionally, the control system 222coordinates with the controller of the electrolyte replenishing system220 to provide the electrolyte for the electroplating process.

[0142] The following is a description of a typical wafer electroplatingprocess sequence through the electroplating system platform 200 as shownin FIG. 2. A wafer cassette containing a plurality of wafers is loadedinto the wafer cassette receiving areas 224 in the loading station 210of the electroplating system platform 200. A loading station transferrobot 228 picks up a wafer from a wafer slot in the wafer cassette andplaces the wafer in the wafer orientor 230. The wafer orientor 230determines and orients the wafer to a desired orientation for processingthrough the system. The loading station transfer robot 228 thentransfers the oriented wafer from the wafer orientor 230 and positionsthe wafer in one of the wafer slots in the wafer pass-through cassette238 in the SRD station 212. The mainframe transfer robot 242 picks upthe wafer from the wafer pass-through cassette 238 and positions thewafer for transfer by the flipper robot 248. The flipper robot 248rotates its robot blade below the wafer and picks up wafer frommainframe transfer robot blade. The vacuum suction gripper on theflipper robot blade secures the wafer on the flipper robot blade, andthe flipper robot flips the wafer from a face up position to a face downposition. The flipper robot 248 rotates and positions the wafer facedown in the wafer holder assembly 450. The wafer is positioned below thewafer holder 464 but above the cathode contact ring 466. The flipperrobot 248 then releases the wafer to position the wafer into the cathodecontact ring 466. The wafer holder 464 moves toward the wafer and thevacuum chuck secures the wafer on the wafer holder 464. The bladderassembly 470 on the wafer holder assembly 450 exerts pressure againstthe wafer backside to ensure electrical contact between the waferplating surface and the cathode contact ring 466.

[0143] The head assembly 452 is lowered to a processing position abovethe process kit 420. At this position the wafer is below the upper planeof the weir 478 and contacts the electrolyte contained in the processkit 420. The power supply is activated to supply electrical power (i.e.,voltage and current) to the cathode and the anode to enable theelectroplating process. The electrolyte is typically continually pumpedinto the process kit during the electroplating process. The electricalpower supplied to the cathode and the anode and the flow of theelectrolyte are controlled by the control system 222 to achieve thedesired electroplating results. Preferably, the head assembly is rotatedas the head assembly is lowered and also during the electroplatingprocess.

[0144] After the electroplating process is completed, the head assembly410 raises the wafer holder assembly and removes the wafer from theelectrolyte. Preferably, the head assembly is rotated for a period oftime to enhance removal of residual electrolyte from the wafer holderassembly. The vacuum chuck and the bladder assembly of the wafer holderthen release the wafer from the wafer holder, and the wafer holder israised to allow the flipper robot blade to pick up the processed waferfrom the cathode contact ring. The flipper robot rotates the flipperrobot blade above the backside of the processed wafer in the cathodecontact ring and picks up the wafer using the vacuum suction gripper onthe flipper robot blade. The flipper robot rotates the flipper robotblade with the wafer out of the wafer holder assembly, flips the waferfrom a face-down position to a face-up position, and positions the waferon the mainframe transfer robot blade. The mainframe transfer robot thentransfers and positions the processed wafer above the SRD module 236.The SRD wafer support lifts the wafer, and the mainframe transfer robotblade retracts away from the SRD module 236. The wafer is cleaned in theSRD module using deionized water or a combination of deionized water anda cleaning fluid as described in detail above. The wafer is thenpositioned for transfer out of the SRD module. The loading stationtransfer robot 228 picks up the wafer from the SRD module 236 andtransfers the processed wafer into the RTA chamber 211 for an annealtreatment process to enhance the properties of the deposited materials.The annealed wafer is then transferred out of the RTA chamber 211 by theloading station robot 228 and placed back into the wafer cassette forremoval from the electroplating system. The above-described sequence canbe carried out for a plurality of wafers substantially simultaneously inthe electroplating system platform 200 of the present invention. Also,the electroplating system according to the invention can be adapted toprovide multi-stack wafer processing.

[0145] While the foregoing is directed to the preferred embodiment ofthe present invention, other and further embodiments of the inventionmay be devised without departing from the basic scope thereof. The scopeof the invention is determined by the claims which follow.

1. An electro-chemical plating cell, comprising: a cell body defining afirst fluid volume; an anode positioned in a lower portion of the cellbody; a first membrane positioned across the cell body above the anode,the membrane forming a second fluid volume proximate the anode surfacethat is isolated from the first fluid volume; a first fluid inlet influid communication with the first fluid volume; a second fluid inlet influid communication with the second fluid volume; and a fluid outlet influid communication with the second fluid volume.
 2. Theelectro-chemical plating cell of claim 1, wherein the second fluid inletis positioned to direct fluid around the anode and out the fluid outlet.3. The electro-chemical plating cell of claim 1, further comprising: asupport ring circumscribing the anode; and a second membrane positionedacross the cell body below the anode.
 4. The electro-chemical platingcell of claim 1, further comprising an electrical connection extendingthrough the cell body and contacting the anode.
 5. The electro-chemicalplating cell of claim 1, wherein the first fluid inlet is positionedbelow the anode and configured to direct a plating solution upwardthrough the plating cell toward a substrate being plated.
 6. Theelectro-chemical plating cell of claim 1, further comprising a fluidpermeable diffusion member positioned across the cell body at a positionabove the anode and below an upper overflow weir of the cell body. 7.The electro-chemical plating cell of claim 1, further comprising adegasser in communication with the first fluid inlet.
 8. Theelectro-chemical plating cell of claim 1, wherein the first membranecomprises a hydrophilic porous fluid permeable material.
 9. Theelectro-chemical plating cell of claim 1, wherein the second fluid inletis configured to supply a fluid at a higher pressure than the firstfluid inlet.
 10. The electro-chemical plating cell of claim 1, whereinthe second fluid inlet and the first fluid outlet are configured todirect a fluid over the anode and remove the fluid from the plating cellwithout the fluid contacting the substrate being plated.
 11. Anelectro-chemical plating cell, comprising: a cell body configured tocontain a plating solution and having an opening sized to receive asubstrate therein for plating; an anode positioned in a lower portion ofthe cell body; a first membrane positioned across the cell body abovethe anode, the membrane being positioned to separate the platingsolution in the cell body from a fluid volume adjacent the anode; aplating solution fluid inlet in fluid communication with a platingsolution volume above the membrane; an anode fluid inlet in fluidcommunication with the fluid volume adjacent the anode; and a anodefluid outlet in fluid communication with the fluid volume adjacent theanode.
 12. The electro-chemical plating cell of claim 11, wherein theanode comprises a soluble metal.
 13. The electro-chemical plating cellof claim 11, wherein the first membrane comprises a hydrophilic porousfluid permeable material.
 14. The electro-chemical plating cell of claim11, wherein the anode fluid inlet is configured to provide a higherfluid pressure than the plating solution fluid inlet.
 12. Theelectro-chemical plating cell of claim 11, wherein the opening comprisesa fluid outlet for the plating solution.
 13. The electro-chemicalplating cell of claim 11, further comprising a second membranepositioned across the cell below the anode.
 14. The electro-chemicalplating cell of claim 11, wherein the plating solution inlet isconfigured to supply a plating solution to the plating cell without theplating solution contacting the anode.
 15. The electro-chemical platingcell of claim 11, wherein the fluid volume adjacent the anode isseparated from the plating solution.
 16. An electro-chemical platingcell, comprising: a cell body defining a plating solution fluid volume;an anode positioned in a lower portion of the cell body; a membranepositioned over the anode, the membrane separating an anode fluid volumefrom the plating solution fluid volume; a fluid inlet in communicationwith the anode fluid volume; a fluid outlet in communication with theanode fluid volume; and a plating solution inlet in fluid communicationwith the plating solution volume.
 17. The plating cell of claim 16,wherein the membrane comprises a porous fluid permeable membrane. 18.The plating cell of claim 16, further comprising a filter membranepositioned across the plating solution fluid volume.
 19. The platingcell of claim 16, further comprising an enclosure positioned around aperimeter and bottom portions of the anode.
 20. The plating cell ofclaim 19, wherein the enclosure comprises a plastic ring portionsurrounding the perimeter of the anode and a bottom encapsulationmembrane positioned below the anode.
 21. The plating cell of claim 16,wherein the plating solution inlet is positioned to direct platingsolution upward through the plating cell toward a substrate immersed inthe plating solution volume.
 22. The plating cell of claim 16, whereinthe plating solution inlet and the fluid inlet in fluid communicationwith the anode fluid volume are individually controlled to generate ahigher fluid pressure in the anode fluid volume than in the platingsolution fluid volume.